This invention relates generally to a sealing structure between a rotating component and a stationary component and, more particularly, to a compliant plate seal arrangement that uses features of a labyrinth seal.
Dynamic sealing between a rotor (e.g., rotating shaft) and a stator (e.g., static shell or casing) is an important concern in turbomachinery. Several methods of sealing have been used. In particular, sealing based on flexible members has been used that include seal members such as compliant plate seals and/or brush seals.
Known brush seals include tightly-packed, generally cylindrical bristles that are arranged in a staggered arrangement to reduce leakage. The bristles have a low radial stiffness that allows them to move in the event of a rotor excursion while maintaining a tight clearance during steady state operations. Brush seals, however, are generally effective only below a limited pressure differential across the seal. Because of the generally cylindrical geometry of the bristles, the brush seals tend to have a low stiffness in the axial direction, which limits the maximum operable pressure differential in known brush seals to generally less than 400 psi.
In contrast, at least some known compliant plate seals have a plate-like geometry that has a significantly higher axial stiffness for a comparable radial stiffness and therefore such seals have the capability of being used with larger pressure differentials than known brush seals. Axial leakage, however, remains a problem due to packing of the compliant plates from an inner diameter of the seal to an outer diameter of the seal. More specifically, the compliant plates are packed tightly together with very small gaps between adjacent plates and the inner diameter of the seal, but the gaps between adjacent plates may increase close to the outer diameter of the seal since each seal is curved. Such gaps potentially cause leakage and may offset any benefits of the compliant plate seals as compared to the brush seals.